1. Field of the Invention
The present invention relates to a machine tool having a table adapted to move back and forth with respect to a main spindle on a bed with a workpiece mounted thereon, more particularly to a machine tool having a table adapted to pivot up and down about a pivot shaft extending perpendicularly to the direction of the movement of the table.
2. Description of the Prior Art
One example of a machine tool of the aforesaid type is a vertical machining center 50 as shown in FIG. 5. As shown, the vertical machining center 50 includes a saddle 53 movable back and forth along the X-axis on a column 52 provided upright on a bed 51, a spindle head 54 attached to the saddle 53 and vertically movable along the Z-axis, and a rotatable table 55 which is movable back and forth along the Y-axis on the bed 51. The table 55 is supported pivotally about a pivot shaft extending along the X-axis by a table frame 56 which is movable back and forth along the Y-axis along slideways 57 provided on the bed 51.
The bed 51 has a center trough 51a extending along the Y-axis between the slideways 57, and a chip conveyer is provided in the center trough 51a. Therefore, chips generated by machining of the workpiece fall within the center trough 51a and transported away from a machining space by the chip conveyer.
Extendible covers 58 for covering the slideways 57 are attached to the table frame 56 which is movable back and forth along the Y-axis along the slideways 57 on the bed 51, so that the chips generated by the machining of the workpiece are prevented from adhering on the slideways 57.
In the vertical machining center 50, the table 55 per se is adapted to move along the Y-axis, so that a pivot mechanism such as a reduction gear mechanism and a servo motor for rotating the pivot shaft fixed to the table 55 should be mounted on the table frame 56. Inevitably, cables such as power supply lines for supplying electric power to the pivot mechanism and the servo motor are located within the machining space where the chips are generated. The pivot mechanism including the reduction gear mechanism and the servo motor attached to the table frame 56 may be covered with a cover, but it is impossible to perfectly prevent intrusion of a coolant and the chips.
In order to assuredly introduce the chips generated by the machining of the workpiece into the chip conveyer, the coolant may be sprayed over the periphery of the center trough 51a and the table frame 56. In such a case, there is a high possibility that a cable cover accommodating the cables is exposed to the coolant. This reduces the service life of the cable cover, requiring replacement thereof every several years.
It is therefore an object of the present invention to provide a machine tool which is constructed so that a table pivot mechanism and cables such as power supply lines are protected from chips and a coolant.
In accordance with the present invention to achieve the aforesaid object, there is provided a machine tool of a center trough structure, which comprises: a bed having a trough provided in a widthwise middle portion thereof, and slideways provided thereon on widthwise opposite sides of the trough; a chip conveyer provided in the trough; a rotatable table; a table frame supporting the table pivotally about a pivot axis and movable back and forth along the slideways perpendicularly to the pivot axis of the table on the bed; a pivot mechanism provided on an outer side of the table frame for pivoting the table; and covers attached to the table frame and adapted to be partly extended and partly contracted in directions of the movement of the table frame for covering the slideways and the pivot mechanism.
In the machine tool having the aforesaid construction, the covers adapted to be partly extended and partly contracted in the directions of the movement of the table frame are attached to the table frame so as to cover the table frame slideways and the table pivot mechanism provided on the outer side of the table frame. Therefore, the table pivot mechanism and the table frame slideways are located outside a machining space defined between the covers thereby to be perfectly protected from chips and a coolant in the machining space.
Since the table pivot mechanism is located outside the machining space defined between the covers, cables such as a power supply line connected to a servo motor of the pivot mechanism can be routed outside the machining space. Therefore, not only the pivot mechanism but also the cables can perfectly be protected from the chips and the coolant.
The foregoing and other objects, features and effects of the present invention will become more apparent from the following description of the preferred embodiments with reference to the attached drawings.